Detection of light from transgenic animals carrying a gene encoding a light-generating protein is a powerful tool in diagnostics, drug discovery and medicine that allows for the identification of disease pathways, determination of mechanisms of action, evaluation of efficacy of drug compounds, and monitoring lead candidates' effects on disease progression in living animals. See, e.g., U.S. Pat. Nos. 7,449,615; 7,255,851; 7,198,774; 6,939,533; 6,923,951; 6,916,462; 6,908,605; 6,890,515; 6,649,143; 6,217,847; and 5,650,135.
In the case of bioluminescent proteins a substrate is typically administered to the animal prior to the evaluation. For example, luciferase (e.g., encoded by eukaryotic luc gene), catalyses the oxidation of D-luciferin (D-(−)-2-(6′-hydroxy-2′benzothioazolyl)thiazoline-4-carboxylic acid) in the presence of ATP to generate light signals. The availability of the substrate has been shown to effect photon emission efficiency. See, e.g., Lee et al. (2003) Nuclear Medicine Communications 24:1003-1009; Berger et al. (2008) Eur. J. Nuclear Medicine and Mol. Imaging 35(12):2275-2285. Various derivatives of luciferin have been prepared, including preparations in which luciferin is covalently bonded to a targeting moiety (see, e.g., U.S. Pat. No. 4,665,022) or a fluorescent label (see, e.g., 5-fluoroluciferin available from Promega) as well as 6-substituted D-luciferin esters for use evaluation of pesticides (see, e.g., U.S. Pat. No. 5,374,534).
Despite the wide-spread use of bioluminescent imaging techniques, there remains a need a need for improved methods for detecting, quantifying and validating bioluminescence in living animals.